This application is related to the concurrently filed Cheung Application Ser. No. 752,011 entitled "Expanding Strap Loop Forming And Friction Fusion Machine."
In the past, Signode Corporation, the assignee of the entire interest of the present invention, has developed several processes and machines for forming a strap loop about a package, tensioning the loop, and joining the overlapping portions of the tensioned loop.
Some strapping machines, such as the machine disclosed in the Kobiella U.S. Pat. No. 3,442,203, are of the completely automatic type, i.e., one which automatically feeds a thermoplastic strap around a package from a strap supply source, grips the leading end of the strap, withdraws the standing length of the strap to tension the strap loop, friction-fuses the overlapping portions of the loop, and severs the loop from the standing length of the strap. However, this type of automatic strapping machine has a relatively large, ring-like, rigid chute into which the package is inserted and in which the strap is fed to form a closed loop around the package. With thermoplastic strap, problems have been encountered wherein the strap may buckle or jam in the chute as the strap is fed around the package. This is due to the relatively low column strength of the thermoplastic strap. In addition, a ring-like chute adds considerable bulk to the machine and requires a work space, or operating space, large enough to accommodate the chute and large enough to provide insertion and removal areas for the package.
It would be desirable to devise a strapping method wherein the strap loop could be formed without the need for a large, ring-like chute into which a package must be inserted. Use of such a method would require relatively less space than the present method that requires a chute. Thus, a method that does not require a chute could be performed on a work table or desk and could be used for strapping small packages.
Automatic strapping machines which use ring-like chutes to form the loop about the package are somewhat inefficient with respect to strapping different size packages. For example, if a strapping machine is intended to strap large packages, say 3 feet in diameter, then the strap chute must be at least 3 feet in diameter. If, subsequently, the machine is used to strap much smaller packages, say 1 foot in diameter, then the strap loop formed around the smaller package is initially three feet in diameter and the machine must withdraw a substantial amount of trailing strap during the tensioning process to decrease the diameter of the loop and tighten it about the 1-foot diameter package. This is obviously inefficient. Therefore, it would be desirable to provide a method for forming a strap loop of any desired size. Such a method would advantageously be used in strapping operations where the size of the packages would vary.